The living brains exhibits electrical activity, which vary in strength and frequency over time and from one part of the brain to another. Different frequencies are associated with different moods and changing abilities. A brain wave frequency of 13 hertz or higher is known as “beta-rhythm” and is normally associated with daily activity when all five sensory organs are functioning. A brain wave frequency of 8 to 13 hertz is known as “alpha-rhythm” and is often associated with a relaxed creative state. Brain wave frequencies of 4 to 8 hertz and 0.5 to 4 hertz are known as “theta-rhythm” and “delta-rhythm” respectively. Theta-rhythm is often found in adolescents with learning disorders, and delta-rhythm is typical of normal sleep. Researchers believe that externally creating brain wave frequencies associated with normal or desired behavior, such as externally creating delta-rhythm in someone who has a problem sleeping or alpha-rhythm in someone who has trouble learning, can help bring about such behavior.
Alpha waves are those between 7.5 and thirteen (13) waves per second (Hz). Alpha is usually best seen in the posterior regions of the head on each side, being higher in amplitude on the dominant side. It is brought out by closing the eyes and by relaxation, and abolished by eye opening or alerting by any mechanism (thinking, calculating). It is the major rhythm seen in normal relaxed adults—it is present during most of life especially beyond the thirteenth year when it dominates the resting tracing.
Beta activity is ‘fast’ activity. Its frequency is 14 Hz and higher. It is usually seen on both sides in symmetrical distribution and is most evident frontally. It is accentuated by sedative-hypnotic drugs especially the benzodiazepines and the barbiturates. It may be absent or reduced in areas of cortical damage. It is generally regarded as a normal rhythm. It is the dominant rhythm in patients who are alert or anxious or who have their eyes open.
Theta activity has a frequency of 3.5 to 7.5 Hz and is classed as “slow” activity. It is abnormal in awake adults but is perfectly normal in children up to 13 years and in sleep. It can be seen as a focal disturbance in focal subcortical lesions; it can be seen in generalized distribution in diffuse in diffuse disorder or metabolic encephalopathy or deep midline disorders or some instances of hydrocephalus
Delta activity is 3 Hz or below. It tends to be the highest in amplitude and the slowest waves. It is quite normal and is the dominant rhythm in infants up to one year and in stages 3 and 4 of sleep. It may occur focally with subcortical lesions and in general distribution with diffuse lesions, metabolic encephalopathy hydrocephalus or deep midline lesions. It is usually most prominent frontally in adults and posteriorly in children.
One of the first “brain scan”, the EEG, or electroencephalograph, is still very useful in non-invasively observing the human brain activity. An EEG is a recording of electrical signals from the brain made by hooking up electrodes to the subject's scalp, typically placed on the head in the standard ten-twenty configuration. These electrodes pick up electric signals naturally produced by the brain and send them to galvanometers (amperemeter) that are in turn hooked up to pens, under which graph paper moves continuously. The pens trace the signals onto the graph paper. Modern EEG equipment now uses electronics, such as computer, to store the electric signals instead of using pens and graph papers.
EEGs allow researchers to follow electrical impulses across the surface of the brain and observe changes over split seconds of time. An EEG can show what state a person is in—asleep, awake, anaesthetized—because the characteristic patterns of current differ for each of these states. One important use of EEGs has been to show how long it takes the brain to process various stimuli.
The electrical activity, or EEG, of human brains has traditionally been used as a diagnostic marker for abnormal brain function and related symptomatic dysfunction. Often, traumatic disturbances such as mechanical injury, social stress, emotional stress and chemical exposure cause neurophysiological changes that will manifest as EEG abnormalities. However, disruption of this abnormal EEG activity by the application of external electrical energy, henceforth referred to as a neurostimulation signal, may cause yet further neurophysiological changes in traumatically disturbed brain tissues, as evidenced in an amelioration of the EEG activity, and hence are beneficial to an individual. Such therapeutic intervention has proven useful in pain therapy and in treating a number of non-painful neurological deficits such as depression, attention deficit disorder, and many others.
Therefore, the need and desire is very strong and there has been a great search for techniques and external stimuli which can vary the brain state. Much has been written about the benefits of relaxation and stress reduction. Stress has been shown to contribute to heart attacks, and is known to suppress the normal operation of the immune system, thus leaving the body vulnerable to attack from many serious illnesses. Different approaches have been made with respect to varying the brain state of a person. For example, various audio systems are commercially sold using subliminal messages in order to coax the brain into a different state.
There are known consciousness state inducing techniques. For example the use of audio generators to induce a state of consciousness known as sleep. In one type of technique exemplified in these patents, generated audio signals include pleasing and harmonious study sounds or vibrations, fixed frequency signals which are buried cyclically with respect to amplitude, and repetitive sounds such as the falling of rain on the roof and the sighing wind through the trees.
There is a method of inducing sleep by generation of an audible or tactual signal which is related to the physiological process of heartbeat and respiration. In this method, the pitch and amplitude of a pleasing audio signal are varied at a rate somewhat slower than either the rate of heartbeat or the rate of respiration. As a result, heartbeat and respiration tend to synchronize with the audio signal, thus lowering heartbeat and respiration rates and inducing sleep.
Of course, there are other naturally-occurring sounds which have been recorded, and which are not varied, but which instead induce a state of relaxation which leads to sleep for a similar reason. For example, the pounding of waves on a shore line occurs at a frequency generally lower than that of heartbeat or respiration, and induces a state of relaxation.
It is indicated that a beat frequency can be produced inside of the brain by supplying signals of different frequencies to the two ears of a person. The binaural beat phenomenon was discovered in 1839 by H. W. Dove, a German experimenter. Generally, this phenomenon works as follows. When an individual receives signals of two different frequencies, one signal to each ear, the individual's brain detects a phase difference or differences between these signals. When these signals are naturally occurring, the detected phased difference provides directional information to the higher centers of the brain. However, if these signals are provided through speakers or stereo earphones, the phase difference is detected as an anomaly. The resulting imposition of a consistent phase difference between the incoming signals causes the binaural beat in an amplitude modulated standing wave, within each superior olivary nucleus (sound processing center) of the brain. It is not possible to generate a binaural beat through an electronically mixed signal; rather, the action of both ears is required for detection of this beat.
Binaural beats are auditory brainstem responses which originate in the superior olivary nucleus of each hemisphere. They result from the interaction of two different auditory impulses, originating in opposite ears, below 1000 Hz and which differ in frequency between one and 30 Hz. For example, if a pure tone of 400 Hz is presented to the right ear and a pure tone of 410 Hz is presented simultaneously to the left ear, an amplitude modulated standing wave of 10 Hz, the difference between the two tones, is experienced as the two wave forms mesh in and out of phase within the superior olivary nuclei. This binaural beat is not heard in the ordinary sense of the word (the human range of hearing is from 20-20,000 Hz). It is perceived as an auditory beat and theoretically can be used to entrain specific neural rhythms through the frequency-following response (FFR)—the tendency for cortical potentials to entrain to or resonate at the frequency of an external stimulus. Thus, it is theoretically possible to utilize a specific binaural-beat frequency as a consciousness management technique to entrain a specific cortical rhythm.
When signals of two different frequencies are presented, one to each ear, the brain detects phase differences between these signals. Under natural circumstances a detected phase difference would provide directional information. The brain processes this anomalous information differently when these phase differences are heard with stereo headphones or speakers. A perceptual integration of the two signals takes place, producing the sensation of a third “beat” frequency. The difference between the signals waxes and wanes as the two different input frequencies mesh in and out of phase. As a result of these constantly increasing and decreasing differences, an amplitude-modulated standing wave—the binaural beat—is heard. The binaural beat is perceived as a fluctuating rhythm at the frequency of the difference between the two auditory inputs.
As a result, binaural beats are produced and are perceived by the brain as a result of the interaction of auditory signals within the brain. Such binaural beats are not produced outside of the brain as a result of the two audio signals of different frequencies. In a sense, the binaural beats are similar to beat frequency oscillations produced by a heterodyne effect, but occurring within the brain itself. However, the article discusses the use of such binaural beats in a strobe-type manner. In other words, if the brain is operating at one frequency, binaural beats of a fixed frequency are produced within the brain so as to entice the brain to change its frequency to that of the binaural beats and thereby change the brain state.
The binaural beat phenomenon described above also can create a frequency entrainment effect. If a binaural beat is within the range of brain wave frequencies, generally less than 30 cycles per second, the binaural beat will become an entrainment environment. This effect has been used to study states of consciousness, to improve therapeutic intervention techniques, and to enhance educational environments.
As the brain slows from beta to alpha to theta to delta, there is a corresponding increase in balance between the two hemispheres of the brain. This balanced brain state is called brain synchnony, or brain synchnonization. Normally, the brain waves exhibit asymmetrical patterns with one hemisphere dominant over the other. However, the balanced brain state offers deep tranquility, flashes of creative insight, euphoria, intensely focus attention, and enhanced learning abilities. Thus it is important for the creative activity of the individual to have a “correct” balance and communication between the brain halves.